Dividends (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Oct. 31, 2013	Oct. 31, 2012	Oct. 31, 2013	Oct. 31, 2012
Dividends [Abstract]
Dividends paid	$ 4,367	$ 3,812	$ 13,094	$ 11,430
Cash dividends paid per common share (in dollars per share)	$ 0.12	$ 0.105	$ 0.36	$ 0.315